Photo: Matthew Shepherd
Summaries of Published Studies of Conservation Benefits of Reduced Mowing
Larson et al (2014): Pollinators were recorded visiting dandelions (Taraxacum officinale) and white clover (Trifolium repens) in urban and suburban lawns in central Kentucky. The primary study period was May and early June, though some surveys of white clover were done in August. In total, 26 bee species were recorded. The dandelions had 20 species, of which nine were early emerging mining bees (Andrena, also called tickle bees) and the clover had 12. For butterflies, dandelions were visited by one species and the clover by six. The authors highlight the risk from insecticides, and note that “awareness of the diverse pollinator assemblages of flowering lawn weeds” might encourage a move toward more pollinator-friendly and sustainable gardening.
Lerman et al (2018): This study explored whether different lawn mowing frequencies (every week, every two weeks, and every three weeks) influenced bee abundance and diversity in suburban yards in Massachusetts. Mowing every three weeks resulted in more than double the number of flowers available in lawns, and increased bee diversity—yet lowered overall bee abundance versus the every-two-weeks strategy. Lerman and her colleagues documented a staggering 93 species of bees, with supplemental observations bringing the total number to 111 bee species—nearly a quarter of all bee species native to the area!
Proske et al (2022): This paper was a meta-analysis that looked at results of many published and unpublished studies from Europe and North America. They found a significant increase in both abundance and species richness of butterflies and bees, as well as other insect groups (grasshoppers, crickets, and true bugs) in less-frequently mowed lawns. They also found a decrease in abundance of centipedes, millipedes, spiders, and ticks and mites, and noted, “manicured lawns disproportionately favor the abundance of ‘pest’ species.” For greatest benefit, the authors recommended that grass and meadows should only be mowed once or twice a year, and the first mowing is delayed until July—which may be far later and less frequent that most people are comfortable with! However, they also found that the size of the site had no influence on the benefits of reduced mowing. Even small patches had greater diversity.
Wastian et al (2016): By comparing intensely mowed lawns (mowed 12 times per year) with meadows under reduced maintenance (mowed only twice per year), the authors found that the number of bee species visiting the intensely mowed lawns was significantly lower. Of the 43 species of bees recorded, only 22 were on intensely mowed lawns, and of the six at-risk species observed, none were on frequently mowed lawns.
Watson et al (2019): Another meta-analysis of numerous studies from North America and Europe that looked at the effects of mowing on various insect groups. The conclusions were that increased mowing intensity resulted in a significant negative effect on plant diversity and insect diversity, and a moderate increase in pest abundance. It also found that by reducing mowing frequency from 15 to 10 times per year, park managers may have cost savings of up to 36%.